Multifrequency oscillator



. H. A. AFFEL MULTIFREQUENCY OSCILLATOR Filed Sept. 19. 1924 A TTORNE YPatented oei. ze, 192e.

lUNITE!) SiATiFiS HERMAN A. AFFEL, I' MAFLEWOOD,'NEV JERSEY, ASSIGNOR TOAIVEBIICAI TELE- PHONE'ANDTELEGRAPH COMPANY, A CORPORATION OF NEW' YORK;

MULTIFREQUENCY OSCILLATR.

Applic'atonfiled September 19, 1924. Serial No. 738,698.

'This invention relates to oscillation generators, and more particularlyto an oscillation generator capable of producing a plurality, offrequencies. V

While multi-frequency generators l have 'been produced heretofore, suchgenerators h'ave, for the most part, been of the type in 'which lthevvarious frequencies generated are related toeach otheras harmonics of acomnl n'ionfundam'ental. It is an object of the 'present inventiontoproduce a multi-frequencygenerator in which the various frequenciesproduced 'may be related in anonharmonic' manner and yet may bedefinitely iscont'rolled by a principal frequency. Another object of theinvention is to produce 4an oscillatingA circuit including a completeoscillating path in which the frequency changes 'from point to' point inthe path a lplurality lof times. Another object of the invention is toproduce an oscillating circuit in which a high degree of stability isattained. 'Still another object of the invention is to produceanoscillating circuit in which, ,y y

' less than the Vdifference :between the frequencies f f1 and f2, and"consequently, `the cuni yby theadjustment of a single timing element, aplurality 'of diderent frequencies may all be simultaneously changed.

These objects and other objects of the in- 4`fvention are attained bythe"arrangenients disclosed, which are fullyA set forth in the followingdescription and illustratedin the accompanying draw'ing,"li`igures l and2 of Vwhich are circuit :diagrams showingmtwo modifications Voff/theinyenticn. l

Referring to Fig. l,"Mand`M designate, respectively, f the'balanced typehaving their input circuits connected' to frequency sources f1 andf2,"re'spective`ly. Y Owing to the balanced connections of themodulators, the'fr'equen'cies .pfff and f2 appliedtd the two modulatorswill be suppressed in the output circuit'an'dwill net betransmitted.'The output `circuit of 'the modulator M- is connectedv tothe inputcircuit of the" modulator throughtwo parallel branches, oneincluding thetuned selective circuit S1 and the `other including a A*lowfpassfilterSa. The output `('zircuit of the modulator M is connected with theinput filter S2`liayin'g its cut-off point' so located as to pass thefrequencies flj and f2.

The circuit arrangement above described constitutes a generator ofoscillations and at Adifferent points inthe' circuit four di iferent twovacuum tube modulators circuit of the modulator l/ through a bandlgenerated frequencies may be taltenf dif.

For this purpose, ahigh pass 'filter Sli'and a low pass lter S3 areconnectedito they output circuit of the modulator M, anda high passfilter S2 anda low pass filter Sjareconnected to the outputl circuit4 ofthemodulator vtuned circuit, these yoscillations will beimto theunmodulatedV carrier f1.

pressed upo'n the 'modulator-lifts beat with t the carrier frequency f1,thereby producing sum and difference frequencies )f1-Ht and /L'l-a, aswell as a frequency `corresponding The frequency f1 is suppressed byreason of the bal ance of the modulator circuit and the diff-@v encefrequency fl-a is 'suppl-@Seed by; 'the band filter S2 as this frequencyfalls below its lower cut-.off point. The frequency ct is frequency fl-l-c vpasses through the baud filter S2 and is rimpressed upon themodulator fM".l VThe frequency /f'l-l-ct 'beats-with the frequency f2 toproduce sum and difference frequencies. lf b bextakeii as the differencebetweent f1 and f2, the e'lipression ffl-o may be substituted forthe'frequency f2. `The the difference frequencywill be b-a. l'Theuninodulated component corresponding to frequency f2 is suppressedbythe: balanced circuit of the modulator. `Y The low pass vlillter S3 inthe output circuit has its cut-off point below the frequency a, and ifthe fijequencies f1 and y, are Vso chosen that?) is greater' than a andZi-q is less than ci, lthe difference frequency bi-ct produced'by themodulator M in its outpi'it'circuit will be lwith'the carrierlfreque'ncyf1, a sum 1frequency .fl-{#{bla} and a ldifference "frequency f1-(b-a)are produced. The difference frequency falls below the lower cutoffpoint of the band filter S2 but the sum frequency fl-i-(-a) fallsbetween the cutoff points f1 and f2 of said filter, so that the sumfrequency only is transmitted. The sum frequency in turn is impressedupon the modulator. M, thereby beating with the frequency f2 to producea sum frequency 2f1+2ba and a difference frequency a. The sum frequencyis suppressed as it falls above the upper cut-off point of the filter S3and is too high to be passed to the tuned circuit S1. The differencefrequency a, however, passes through the tuned circuit S1 and starts thecycle of operations above described anew. u It will be seen that in thecomplete oscillating circuit the frequency is changed four times andthat the four frequencies thus produced need not bear a harmonicrelation to each other. The primary frequency ct is independent of thefrequencies f, and f2 supplied to the modulators and is determined onlyby the tuning of the selective circuit S1. Consequently, the frequenciesf, and 'f2 may vary within limits from time to time without producingany change in the primary frequency a. The otherv three frequenciesgenerated, namely, ffl-a, b-e and fl-l-(b-e) are all functions of theprimary frequency a but need not be harmonics thereof. In the assumedcase, the generated frequency b-a is less than a and the other twogenerated frequencies are greater. It will also be noted that the energymust be transmitted twice over the same path in order to complete onecycle of the action. The various frequencies transmitted during thedifferent operations of the cycle are indicated by the schematic diagramshown in Fig. 1 in the interior of the main circuit layout.

Another characteristic of the arrangement disclosed is that all four ofthe frequencies generated may be changed (within limits) by merelyadjusting the tuned circuit S1. Y

This follows from the fact that the frequencies f1+a, -a and fl-i-(b-a)are all functions of the primary frequency a, and since the frequency ais independent of the frequencies f, and f2 and is determined only bythe tuning of the selective circuit S1, it follows at once that allAfour of the frequencies generated will depend upon the tuning of thecircuit S1.

The four frequencies generated may be readily taken off from theoscillating system by means of combinations of high pass and low passfilters as indicated in the diagram. Since only the frequencies a andb-(r appear in the output circuit of the modulator M, these twofrequencies may be taken off through high pass filter S1', and low passfilter Sa', respectively, thesefilters being connected in branchesleading from the output circuit of the modulator M. The lower cutoffpoint of the high pass filter and 'the upper cut-off point of the lowpass filter should be brought as close to each other as is consstentwith selectivity and the two frequencies representing these cut-offpoints should be intermediate between the normal values of frequencies aand b-a, so as to allow for any change in the frequencies due toadjustments of the tuned circuit S,. Y The vfrequencies fl-l-q andffl-(bwa) appear only in the output circuit of the modulator M and canbe taken off through the high pass filter S2 and low pass filter S4,respectively, these kfilters being connected in branches associated withthe output circuit of the modulator M. Here again the lower cut-offfrequency of the filter S2 and the upper cut-off frequency of the filterS4 should be as close together as is consistent with the properselectivity and t" the two cut-off frequencies should also be locatedintermediate between the normal values of fla-a and ffl-(bua) to permitof a desired amount of change in the frequencies by changing` the tuningof the circuit S1.

A modified arrangement is shown in Fig. 2, in which a tuned circuitselective of the frequency b-q is substituted for the low pass filterAlso, instead of the band lilter S2 of Fig. l, a pair of branchesincluding tuned circuits S2 and S4, selective of frequencies fl-l-q andf1-{-(-a), respectively, are used.

The operation will be similar to that described in connection with Fig.l but it will be noted that in this arrangement, if .the selectivecircuits S2, S3 and S4 are sharply tuned, the generator will tend to bemore stable. This follows from the fact that each one of the fourfrequencies generated depends upon the setting of four dilere'nt tunedcircuits selective of four different frequencies. For example, theprimary frequency a depends not only upon the setting of the selectivecircuit Sl but upon the setting of the other three selective circuitsS2, S3 and S4 as well. Similarly, the other three frequencies likewisemutually depend upon all four tuned circuits.

It will be obvious that the general principles hereindisclosed may beembodied in many other organizations widely dierent from thoseillustrated without departing from the spirit of the invention asdefined in the appended claims.

What is claimed is:

l. In a multi-frequency oscillation generator, a closed path in whichthe oscillations flow, means to determine a primary frequency in saidpath, and means to produce a plurality of changes in frequency as theenergy flows over said path, the frequencies resulting from suchfrequency changes not being related to the primary frequency asharmonics thereof.

ino

2. In a multi-frequency generator, a closed path through which thevgenerated frequencies iow, means in said path to determine a primaryfrequency, and means in said path to produce successive changes in thefre quency, the final change being a change to the primary frequency,and a complete cycle of changes involving a transmission of energy morethan once about said path.

3. In a multi-frequency generator, a closed path over which thefrequencies generated flow, means in said path to determine a primaryfrequency, means in said path to step upl the frequency, and means insaid path to step down the frequency, the successive frequency changesthus produced beingso related that the energy Will flow a plurality oftimes about said path in order to complete a cycle.

4. In a multi-frequency generator, a closed path over which thefrequencies generated flow, means in said path to determine a primaryfrequency, means in said path to combine said primary frequency With anauxiliary frequency to produce a sum frequency, and means in said pathto combine said sum frequency with another auxiliary frequency toproduce a difference frequency, whereby a plurality of said frequencychanges occur as the energy traverses said path.

5. In a multi-frequency generator, a closed path over which thefrequencies generated flow, means in said path to determine a primaryfrequency, means in said path to combine said primary frequency With anauxiliary frequency to -produce a sum frequency, and means in said pathto combine said sum frequency With another auxiliary frequency toproduce a dierence frequency, whereby a plurality of said frequencychanges occur as the energy traverses said path, the last frequencychange being a change to the primary frequency, said auxiliaryfrequencies being so related to each other that the energy will flowover said path a plurality of times in order to complete a cycle.

6. In ya multi-frequency oscillator, a closed path over which theoscillations generated flow. a pair of frequency changing andtranslating devices in said path, a plurality of selective branches ineach portion of the path connecting the output of one translating deviceto the input of the successive translating device, one of the selectivedevices in one of the branches of one of said portions of said pathdetermining one of the frequencies generated independently of theselective devices in other branches.

7. In a multi-frequency oscillator, a closed path over Which theoscillations generated flow, a pair of frequency changing andtranslating devices in said path, a plurality of selective branches ineach portion of the path connecting the output of one translating deviceto the input of the successive translating device, one of the selectivedevices in one of the branches of one of said portions of said pathdetermining one of the frequencies generated independently of theselective devices in other branches, said selective device determiningall the other frequencies circulating in said path.

In testimony whereof, I have signed my name to this specification this18th day of September, 1924.

HERMAN A. AFFEL.

